Kamiki Boulder Skip
At the beginning of the game, Ammy is prevented from leaving cursed Kamiki to Shinshu by a large boulder. It's possible to skip this boulder via KT's. This is possible because the loading zone still exists behind the boulder.
It is performed by doing a wall jump to the left of the boulder and then doing a KT arcing around an invisible wall that extends higher than the boulders themselves. It is possible to get stuck inside the boulder, but with successive KTs you can still escape.
Reverse Boulder Skip
In NG+ All Brushes you have to return to Kamiki after getting Bloom to get Water Lily and Sunrise. However, the boulder is still there, so you must do an almost-blind KT to clip through the boulder and get on top of it. Going to the right side and holding backwards during the wall jump keeps the camera closer to Ammy, avoiding a completely blind KT.
Because you never go through the sequence of restoring Kamiki, some properties of cursed Kamiki remain when returning. There are still whisps of mist, and some of the villagers are still petrified. The cherry blossoms can still be bloomed.
Because Mushi's Mom remains petrified, you can dig up all the turnips without obstruction. You can still present the Oddly-Shaped Turnip to Mushi, despite him being petrified. During the dialogue, Mushi will still move his head as though he were restored.